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382 lines
8.5 KiB
ReStructuredText
===============
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Iforce Protocol
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===============
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:Author: Johann Deneux <johann.deneux@gmail.com>
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Home page at `<http://web.archive.org/web/*/http://www.esil.univ-mrs.fr>`_
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:Additions: by Vojtech Pavlik.
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Introduction
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============
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This document describes what I managed to discover about the protocol used to
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specify force effects to I-Force 2.0 devices. None of this information comes
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from Immerse. That's why you should not trust what is written in this
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document. This document is intended to help understanding the protocol.
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This is not a reference. Comments and corrections are welcome. To contact me,
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send an email to: johann.deneux@gmail.com
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.. warning::
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I shall not be held responsible for any damage or harm caused if you try to
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send data to your I-Force device based on what you read in this document.
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Preliminary Notes
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=================
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All values are hexadecimal with big-endian encoding (msb on the left). Beware,
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values inside packets are encoded using little-endian. Bytes whose roles are
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unknown are marked ??? Information that needs deeper inspection is marked (?)
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General form of a packet
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------------------------
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This is how packets look when the device uses the rs232 to communicate.
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== == === ==== ==
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2B OP LEN DATA CS
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== == === ==== ==
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CS is the checksum. It is equal to the exclusive or of all bytes.
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When using USB:
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== ====
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OP DATA
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== ====
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The 2B, LEN and CS fields have disappeared, probably because USB handles
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frames and data corruption is handled or unsignificant.
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First, I describe effects that are sent by the device to the computer
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Device input state
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==================
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This packet is used to indicate the state of each button and the value of each
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axis::
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OP= 01 for a joystick, 03 for a wheel
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LEN= Varies from device to device
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00 X-Axis lsb
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01 X-Axis msb
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02 Y-Axis lsb, or gas pedal for a wheel
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03 Y-Axis msb, or brake pedal for a wheel
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04 Throttle
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05 Buttons
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06 Lower 4 bits: Buttons
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Upper 4 bits: Hat
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07 Rudder
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Device effects states
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=====================
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::
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OP= 02
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LEN= Varies
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00 ? Bit 1 (Value 2) is the value of the deadman switch
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01 Bit 8 is set if the effect is playing. Bits 0 to 7 are the effect id.
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02 ??
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03 Address of parameter block changed (lsb)
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04 Address of parameter block changed (msb)
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05 Address of second parameter block changed (lsb)
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... depending on the number of parameter blocks updated
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Force effect
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------------
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::
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OP= 01
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LEN= 0e
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00 Channel (when playing several effects at the same time, each must
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be assigned a channel)
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01 Wave form
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Val 00 Constant
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Val 20 Square
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Val 21 Triangle
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Val 22 Sine
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Val 23 Sawtooth up
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Val 24 Sawtooth down
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Val 40 Spring (Force = f(pos))
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Val 41 Friction (Force = f(velocity)) and Inertia
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(Force = f(acceleration))
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02 Axes affected and trigger
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Bits 4-7: Val 2 = effect along one axis. Byte 05 indicates direction
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Val 4 = X axis only. Byte 05 must contain 5a
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Val 8 = Y axis only. Byte 05 must contain b4
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Val c = X and Y axes. Bytes 05 must contain 60
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Bits 0-3: Val 0 = No trigger
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Val x+1 = Button x triggers the effect
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When the whole byte is 0, cancel the previously set trigger
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03-04 Duration of effect (little endian encoding, in ms)
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05 Direction of effect, if applicable. Else, see 02 for value to assign.
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06-07 Minimum time between triggering.
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08-09 Address of periodicity or magnitude parameters
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0a-0b Address of attack and fade parameters, or ffff if none.
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*or*
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08-09 Address of interactive parameters for X-axis,
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or ffff if not applicable
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0a-0b Address of interactive parameters for Y-axis,
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or ffff if not applicable
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0c-0d Delay before execution of effect (little endian encoding, in ms)
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Time based parameters
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---------------------
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Attack and fade
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^^^^^^^^^^^^^^^
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::
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OP= 02
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LEN= 08
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00-01 Address where to store the parameters
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02-03 Duration of attack (little endian encoding, in ms)
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04 Level at end of attack. Signed byte.
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05-06 Duration of fade.
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07 Level at end of fade.
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Magnitude
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^^^^^^^^^
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::
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OP= 03
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LEN= 03
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00-01 Address
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02 Level. Signed byte.
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Periodicity
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^^^^^^^^^^^
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::
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OP= 04
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LEN= 07
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00-01 Address
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02 Magnitude. Signed byte.
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03 Offset. Signed byte.
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04 Phase. Val 00 = 0 deg, Val 40 = 90 degs.
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05-06 Period (little endian encoding, in ms)
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Interactive parameters
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----------------------
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::
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OP= 05
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LEN= 0a
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00-01 Address
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02 Positive Coeff
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03 Negative Coeff
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04+05 Offset (center)
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06+07 Dead band (Val 01F4 = 5000 (decimal))
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08 Positive saturation (Val 0a = 1000 (decimal) Val 64 = 10000 (decimal))
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09 Negative saturation
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The encoding is a bit funny here: For coeffs, these are signed values. The
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maximum value is 64 (100 decimal), the min is 9c.
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For the offset, the minimum value is FE0C, the maximum value is 01F4.
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For the deadband, the minimum value is 0, the max is 03E8.
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Controls
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--------
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::
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OP= 41
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LEN= 03
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00 Channel
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01 Start/Stop
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Val 00: Stop
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Val 01: Start and play once.
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Val 41: Start and play n times (See byte 02 below)
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02 Number of iterations n.
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Init
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----
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Querying features
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^^^^^^^^^^^^^^^^^
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::
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OP= ff
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Query command. Length varies according to the query type.
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The general format of this packet is:
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ff 01 QUERY [INDEX] CHECKSUM
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responses are of the same form:
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FF LEN QUERY VALUE_QUERIED CHECKSUM2
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where LEN = 1 + length(VALUE_QUERIED)
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Query ram size
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~~~~~~~~~~~~~~
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::
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QUERY = 42 ('B'uffer size)
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The device should reply with the same packet plus two additional bytes
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containing the size of the memory:
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ff 03 42 03 e8 CS would mean that the device has 1000 bytes of ram available.
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Query number of effects
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~~~~~~~~~~~~~~~~~~~~~~~
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::
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QUERY = 4e ('N'umber of effects)
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The device should respond by sending the number of effects that can be played
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at the same time (one byte)
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ff 02 4e 14 CS would stand for 20 effects.
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Vendor's id
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~~~~~~~~~~~
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::
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QUERY = 4d ('M'anufacturer)
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Query the vendors'id (2 bytes)
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Product id
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~~~~~~~~~~
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QUERY = 50 ('P'roduct)
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Query the product id (2 bytes)
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Open device
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~~~~~~~~~~~
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::
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QUERY = 4f ('O'pen)
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No data returned.
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Close device
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~~~~~~~~~~~~
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::
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QUERY = 43 ('C')lose
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No data returned.
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Query effect
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~~~~~~~~~~~~
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::
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QUERY = 45 ('E')
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Send effect type.
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Returns nonzero if supported (2 bytes)
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Firmware Version
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~~~~~~~~~~~~~~~~
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::
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QUERY = 56 ('V'ersion)
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Sends back 3 bytes - major, minor, subminor
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Initialisation of the device
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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Set Control
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~~~~~~~~~~~
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.. note::
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Device dependent, can be different on different models!
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OP= 40 <idx> <val> [<val>]
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LEN= 2 or 3
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00 Idx
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Idx 00 Set dead zone (0..2048)
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Idx 01 Ignore Deadman sensor (0..1)
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Idx 02 Enable comm watchdog (0..1)
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Idx 03 Set the strength of the spring (0..100)
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Idx 04 Enable or disable the spring (0/1)
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Idx 05 Set axis saturation threshold (0..2048)
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Set Effect State
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~~~~~~~~~~~~~~~~
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::
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OP= 42 <val>
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LEN= 1
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00 State
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Bit 3 Pause force feedback
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Bit 2 Enable force feedback
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Bit 0 Stop all effects
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Set overall
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~~~~~~~~~~~
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::
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OP= 43 <val>
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LEN= 1
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00 Gain
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Val 00 = 0%
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Val 40 = 50%
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Val 80 = 100%
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Parameter memory
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----------------
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Each device has a certain amount of memory to store parameters of effects.
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The amount of RAM may vary, I encountered values from 200 to 1000 bytes. Below
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is the amount of memory apparently needed for every set of parameters:
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- period : 0c
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- magnitude : 02
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- attack and fade : 0e
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- interactive : 08
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Appendix: How to study the protocol?
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====================================
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1. Generate effects using the force editor provided with the DirectX SDK, or
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use Immersion Studio (freely available at their web site in the developer section:
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www.immersion.com)
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2. Start a soft spying RS232 or USB (depending on where you connected your
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joystick/wheel). I used ComPortSpy from fCoder (alpha version!)
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3. Play the effect, and watch what happens on the spy screen.
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A few words about ComPortSpy:
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At first glance, this software seems, hum, well... buggy. In fact, data appear with a
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few seconds latency. Personally, I restart it every time I play an effect.
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Remember it's free (as in free beer) and alpha!
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URLS
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====
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Check http://www.immerse.com for Immersion Studio,
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and http://www.fcoder.com for ComPortSpy.
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I-Force is trademark of Immersion Corp.
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